<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        p{}
        /* id不许重复 
            为js服务
        */
        #p1{
            background-color: red;
        }
        /* 类选择器 允许重复 */
        .wen{
            background-color: yellow;
        }
    </style>
</head>
<body>
    <p id="p1">1111</p>
    <!-- <p id="p1">2222</p> -->
     <p class="wen">鲁迅</p>
     <p class="wen">李清照</p>
     <p>鲁智深</p>
     <hr>
     <style>
        [blood]{
            background-color: pink;
        }
        [blood="30"]{
            color: blue;
        }
        [class="wen"]{
            width: 100px;
        }
     </style>
     <p blood="20">aaa</p>
     <p blood="30">bbb</p>
     <p>ccc</p>
</body>
</html>